There has been conventionally used a studless tire having relatively soft tread rubber as a tire for safely running on ice, as well as a dry road surface. It is known that on-ice performance of a tire improves when tread rubber of the tire is made relatively soft. However, a tire having soft tread rubber generally has a problem in that the tire exhibits poor wear resistance on a dry road surface. In short, on-ice performance and wear resistance of a tire cannot be improved at the same time in a compatible manner.
In this connection, PTL1 proposes a rubber composition containing 0.5-20 parts by weight of potassium titanate fiber and 5-200 parts by weight of carbon black having 100-300 mg/g of iodine adsorption amount, with respect to 100 parts by weight of a rubber component comprising natural rubber and butadiene rubber. PTL1 reports that use of the rubber composition in a cap tread layer of two-layered tread including cap tread and base tread improves performance on ice (and snow), while well suppressing deterioration of wear resistance of the tire.